PHASE EQUILIBRIA STUDIES WITH BROMINE
A THESIS
Presented to
the Facility of the Graduate Division
Henry Dodson Reese Page
In Partial Fulfillment
of the Requirements for the Degree
Master of Science in Chemistry
Georgia Institute of Technology
September 19$2
(
PHASE EQUILIBRIA STUDIES WITH BROMINE
Approved:
Date Approved by Chairman
iii
ACKNOWLEDGMENTS
I wish to express my appreciation to Dr.
M. Spicer, upon
•whose suggestion and under whose supervision this investigation has been
conducted,
I should l i k e to express my appreciation to the "Kinetic"
Chemicals Division of DuPont for furnishing without charge one of the
solvents used in t h i s investigation.
Also, I wish to thank Mr. A, M.
Whaley of Halogen Chemicals, Inc., upon whose advice two of the solvents
were selected.
iv
TABLE OF CONTENTS
Page
APPROVAL SHEET
ii
ACKNOWLEDGMENTS
iii
LIST OF TABLES
vi
LIST OF FIGURES
vii
ABSTRACT
viii
Chapter
I,
II.
INTRODUCTION
1
APPARATUS AND MATERIALS
3
A.
Apparatus
3
1 . Equilibrium S t i l l
3
2. The Large Fractionating Column
6
3. The Small Fractionating Column
6
iu Apparatus for Measuring Volume
Change on Mixing
7
B. Materials
1* Bromine
••
•
2. Solvents
III.
PROCEDURE AND RESULTS
A,
8
8
9
General Procedure for Operating the
Equilibrium S t i l l
B.
•
8
General Method of Analysis
9
12
Chapter
Page
C. The System Bromine- Trichloromonofluorome thane
D.
The System Bromine- 1,1-dichloro2,2-difluoroethane
E.
DISCUSSION OF RESULTS.
APPENDIX I .
16
The System Bromine- 1,2,2-trichloro1,1-di fluoroe thane
IV.
Ih
TABLES AND FIGURES
1°
23
31
APPENDIX I I . SAMPLE CALCULATIONS
h9
BIBLIOGRAPHY
53
vi
LIST OF TABLES
Table
1.
Page
Vapor-Liquid Equilibria Data for the System
Br omine-Trichloromonofluoromethane
2.
31
Fractional D i s t i l l a t i o n of
l,l-dichloro-2,2-difluoroe thane
3.
32
Vapor-Liquid Equilibria Data for the System
Bromine- l,l-dichloro-2,2-difluoroethane
U*
33
Fractional D i s t i l l a t i o n of
1,2,2-trichloro-l, 1-difluoroe thane • • •
5.
3U
Vapor-Liquid Equilibria Data for the System
Bromine- l,2,2-trichloro-l,l-difluoroethane
35
6.
Data on Tests for Evidence of Reaction
36
7.
Data on Volume Changes Observed on Mixing*
37
8.
The Physical Properties of
the Systems Investigated
the
Components
of
38
vii
LIST OF FIGURES
Figure
1.
Page
Temperature-Composition Diagram for the
System Br 2 - CCl^F at 760 mm Pressure
2.
3.
39
Vapor-Liquid Equilibrium Diagram for the
System Br 2 - CCI3F at 760 mm Pressure
kO
Fractional D i s t i l l a t i o n of CHC^CHFg
la
Temperature-Composition Diagram for the
System Br2 - CHCI2CHF2 at 760 mm Pressure
$.
hZ
Vapor-Liquid Equilibrium Diagram for the
System Br2 - CHCI2CHF2 at 76O mm Pressure
h3
6.
Fractional D i s t i l l a t i o n of CHC1 CF C1
hh
7«
Temperature-Composition Diagram for the
2
2
System B r - CHC1 CF2C1 at 760 mm Pressure
2
8.
V a p o r - L i q u i d E q u i l i b r i u m Diagram f o r
System
9.
10.
2
Br2 - CHCI2CF2CI
hS
the
at 760 mm Pressure
k&
Equilibrium S t i l l
lfl
Drying Train
1*8
viii
ABSTRACT
PHASE EQUILIBRIA STUDIES WITH BROMINE
A study of the liquid-vapor equilibria of three binary systems,
each consisting of bromine and an organic solvent was made. The ex­
perimentally obtained results were compared with predictions based on
the properties of the components, and on the interaction between the
components of each system as measured by volume change on mixing.
This investigation i s a continuation of work by Spicer and Kruger, and
by Spicer and Meyer. The work was initiated to discover binary azeotropes consisting of one colored and one colorless component. Azeotropes
of t h i s type are valuable i n the study of methods for separating azeotropic mixtures, for the extent of separation can be ascertained merely
by visual observation.
The e q u i l i b r i u m s t i l l used i n t h i s investigation was modified
from a similar s t i l l described by Jones, Schoenborn, and Colbura. A
scale drawing of the modified s t i l l i s presented. A l l equilibria were
studied at 760 mm pressure.
The System Bromine-Trichloromonofluoromethane.—In this system, the
boiling point increases regularly as the mole fraction of bromine i n
the liquid i s increased.
No azeotrope i s formed.
The System Bromine- 1 , l-dichloro-2^ 2-difluoroethane«—In t h i s system
an azeotrope i s formed with a composition of 0.581 mole fraction
ix
b r o m i n e , a n d a b o i l i n g p o i n t o f U°.6° C .
The p e r c e n t i n c r e a s e
in
v o l u m e o n m i x i n g b r o m i n e w i t h t h e s o l v e n t o f t h i s s y s t e m was f o u n d t o
be a b o u t 1.8,
and n o t i c e a b l e c o o l i n g o c c u r r e d .
the deviation from Raoult's law i s greater
This i n d i c a t e s
that
i n t h i s system than i n t h e
system f o l l o w i n g , b u t t h i s c o n c l u s i o n i s i n c o n s i s t e n t w i t h the e s t i m mated i n t e r n a l p r e s s u r e s .
T h i s i n c o n s i s t e n c y c a n be e x p l a i n e d b y t h e
p r o b a b i l i t y o f g r e a t e r hydrogen bonding between t h e molecules o f t h i s
solvent,
t h a n between t h e molecules o f t h e s o l v e n t o f t h e system
following.
The S y s t e m B r o m i n e - 1 , 2 , 2 - t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e # — I n t h i s
an a z e o t r o p e
i s f o r m e d w i t h a c o m p o s i t i o n o f 0.7U7 m o l e
b r o m i n e , a n d a b o i l i n g p o i n t o f 3>U«6° C .
system
fraction
The p e r c e n t i n c r e a s e
in
v o l u m e o n m i x i n g b r o m i n e w i t h t h e s o l v e n t o f t h i s s y s t e m was f o u n d t o
be a b o u t 0 . 3 .
S l i g h t , but noticeable
Measurements
c o o l i n g occurred on m i x i n g .
of the r e f r a c t i v e indices o f the solvents of the
second and t h i r d systems b e f o r e and a f t e r
contact w i t h bromine,
p o r t t h e c o n t e n t i o n t h a t no r e a c t i o n t a k e s p l a c e between t h e s e
v e n t s and b r o m i n e .
The s m o o t h n e s s o f t h e e q u i l i b r i u m c u r v e s
sup­
sol­
is
f u r t h e r evidence t h a t no r e a c t i o n t a k e s p l a c e between t h e s o l v e n t and
bromine i n any o f t h e systems
investigated.
Comparison o f t h e system b r o m i n e - t r i c h l o r o m o n o f l u o r o m e t h a n e and
the system bromine- 1 , 2 , 2 - t r i c h l o r o - l , 1-difluoroethane
with the
system b r o m i n e - b e n z o t r i f l u o r i d e , i n d i c a t e s t h a t b e n z o t r i f l u o r i d e must
be a s s o c i a t e d t o a g r e a t e r
extent than are trichloromonofluoromethane
or 1 , 2 , 2 - t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e *
CHAPTER I
INTRODUCTION
1
PHASE E Q U I L I B R I A STUDIES WITH BROMINE
CHAPTER I
INTRODUCTION
I n t h e development
tures,
o f methods f o r s e p a r a t i n g a z e o t r o p i c
i t i s c o n v e n i e n t t o work w i t h c o n s t a n t b o i l i n g m i x t u r e s
i n g one c o l o r e d c o m p o n e n t ,
c o l o r , b r o m i n e was s u g g e s t e d as a s u i t a b l e
1
Mayer*" f o u n d a z e o t r o p e s
ponent.
Spicer,
Because o f i t s i n t e n s e
component f o r such m i x t u r e s .
i n v e s t i g a t e d t h e system b r o m i n e - c a r b o n
and p r o v e d t h e e x i s t e n c e
contain­
f o r s e p a r a t i o n o f t h e c o l o r e d component c a n
be d e t e r m i n e d b y d i r e c t v i s u a l o b s e r v a t i o n .
Spicer and K r u g e r
mix­
o f an azeotrope
i n t h i s system.
tetrachloride
Spicer and
i n o t h e r systems i n w h i c h b r o m i n e was a com­
T h i s i n v e s t i g a t i o n i s a c o n t i n u a t i o n o f t h e work done b y
Kruger and Meyer.
Because o f t h e h i g h r e a c t i v i t y o f b r o m i n e , a n d t h e f a c t
azeotrope
f o r m a t i o n i s n o t l i k e l y t o o c c u r when t h e d i f f e r e n c e
that
between
b o i l i n g p o i n t s o f t h e components i s l a r g e , ^ t h e c h o i c e o f i n e r t
b r o m i n e s o l v e n t s was d i f f i c u l t .
M. S p i c e r
I t was a l s o d e s i r e d t h a t s u c h s o l v e n t s
a n d J . K r u g e r , J . Am. Chem. S o c . ,
72, 1855 (1950)
hi.
M. S p i c e r a n d L . H . M e y e r , J . A m . Chem. S o c . ,
%.
H . E w e l l , J . M. H a r r i s o n , a n d L . B e r g , I n d . E n g .
36, 871 (19UM
73, 93k (1951)
Chem.,
2
s h o u l d be c o m p l e t e l y m i s c i b l e w i t h b r o m i n e .
completely haolgenated,
The
saturated hydrocarbons.
s e a r c h was b e g u n w i t h
Only t r i c h l o r o m o n o -
f l u o r o m e t h a n e met t h e above r e q u i r e m e n t s , had n o t been p r e v i o u s l y i n ­
v e s t i g a t e d , and was a l s o a v a i l a b l e
o f t h i s compound made a z e o t r o p e
centrations, very unlikely.
a b l e , however,
in quantity.
f o r m a t i o n , except a t low bromine
Because t h i s
i t was u s e d f o r a n i n i t i a l
In general,
The l o w b o i l i n g p o i n t
compound was r e a d i l y
con­
avail­
study.
compounds c o n t a i n i n g a h a l o g e n a t o m o n e a c h c a r b o n
atom w i l l n o t r e a d i l y undergo s u b s t i t u t i o n r e a c t i o n s w i t h b r o m i n e .
has been observed a l s o , t h a t
attached t o the
compounds i n w h i c h t w o f l u o r i n e a t o m s
same c a r b o n , a r e c o n s i d e r a b l y i n c r e a s e d i n
I n v i e w o f t h i s , i t was d e c i d e d t h a t p a r t i a l l y h a l o g e n a t e d
c o n t a i n i n g the CF
absence
2
compounds
the
V a p o r - l i q u i d s t u d i e s w e r e t h e r e f o r e made o n
systems c o n s i s t i n g o f bromine and l , l - d i c h l o r o - 2 , 2 - d i f l u o r o e t h a n e ,
o f bromine and
l,2,2-trichloro-l,l-difluoroethane.
A d e t a i l e d r e p o r t on t h e i n v e s t i g a t i o n o f t h e
e q u i l i b r i a of these
vapor-liquid
t h r e e systems f o l l o w s i n the e n s u i n g
^ A . L . Henne a n d Thomas M i d g l e y ,
Jr.,
J . Am. Chem.
58, 882 (1936).
^J.
are
stability.^
g r o u p w o u l d p r o b a b l y be i n e r t t o b r o m i n e i n
of a catalyst.
It
H. Simons, I n d . Eng. Chem.,
39, 2U0 (19U7).
chapters.
Soc.,
and
CHAPTER
II
APPARATUS AND MATERIALS
3
CHAPTER
II
APPARATUS AND MATERIALS
Apparatus
Equilibrium
Still
A l l l i q u i d - v a p o r e q u i l i b r i a d a t a was o b t a i n e d f r o m an e q u i l i ­
brium s t i l l ,
a s c a l e d r a w i n g o f w h i c h i s shown i n F i g u r e
9*
Originally
t h i s s t i l l was made a c c o r d i n g t o t h e s p e c i f i c a t i o n s o f a s i m i l a r
whose d e s i g n a n d o p e r a t i o n i s d e s c r i b e d b y J o n e s , S c h o e n b o r n ,
Colburn.^
Meyer.
still
and
A d d i t i o n s a n d m o d i f i c a t i o n s w e r e made b y K r u g e r a n d b y
The s t i l l was r e b u i l t f o r t h i s i n v e s t i g a t i o n , a n d
s l i g h t m o d i f i c a t i o n s were
further
made*
As c a n be seen f r o m F i g u r e
structed entirely of glass.
9> t h e e q u i l i b r i u m s t i l l i s
The f l a s h b o i l e r ,
residue
con­
chamber,
and
vapor l i n e each has a s e p a r a t e
c o i l o f nichrome w i r e , connected through
a G e n e r a l R a d i o Company V a r i a c
t o a Sola constant voltage
transformer.
The a d j u s t m e n t o f t h e v o l t a g e a p p l i e d t o t h e r e s i d u e chamber c o i l m u s t
be c a r e f u l l y c o n t r o l l e d , a n d i s d e p e n d e n t
on t h e v o l t a g e a p p l i e d
the f l a s h b o i l e r .
t h e f i r s t s y s t e m had
For t h i s reason, a f t e r
been
s t u d i e d , a v o l t m e t e r h a v i n g a z e r o t o t e n v o l t s s c a l e was p l a c e d
p a r a l l e l w i t h t h e r e s i d u e chamber c o i l .
B o t h t h e r e s i d u e chamber
^ C . A . J o n e s , E . M. S c h o e n b o r n , a n d A . P.
C h e m . , 35, 666
(19U3)
Colburn, Ind.
to
in
and
Eng.
f l a s h b o i l e r c o i l V a r i a c s w e r e c o n n e c t e d t h r o u g h one S u p e r i o r
Electric
Co. Powerstat t o the Sola c o n s t a n t v o l t a g e t r a n s f o r m e r .
this
arrangement,
With
l a r g e f l u c t u a t i o n s i n l i n e v o l t a g e , n o t smoothed o u t b y
t h e c o n s t a n t v o l t a g e t r a n s f o r m e r , c o u l d be q u i c k l y c o m p e n s a t e d f o r
by
a d j u s t i n g the Powerstat u n t i l the voltmeter returned t o a reading
p r e v i o u s l y determined as being c o r r e c t .
The r e s i d u e chamber a n d v a p o r l i n e w e r e c o v e r e d w i t h i n s u l a t i o n
formed f r o m a s b e s t o s p a s t e , e x c e p t f o r a s m a l l window on t h e
residue
chamber, p r o v i d e d so t h a t t h e l i q u i d l e v e l c o u l d be o b s e r v e d .
A l a r g e g l a s s t a n k , n o t shown i n F i g u r e 9,
crushed i c e .
was k e p t f u l l
of
C o l d w a t e r f r o m t h e m e l t i n g i c e was pumped t h r o u g h t h e
t w o c o n d e n s e r s , a l l o w e d t o t r i c k l e o v e r t h e c r u s h e d i c e , and r e c i r c u ­
lated.
I n studying the f i r s t
s y s t e m , i t was n e c e s s a r y t o p l a c e
c o o l i n g c o i l of glass around the lower p o r t i o n of the residue
a n d t o pump i c e w a t e r t h r o u g h t h i s a l s o .
p o i n t o f ihe
chamber,
T h i s was b e c a u s e t h e b o i l i n g
s o l v e n t , t r i c h l o r o m o n o f l u o r o m e t h a n e , was s o m e t i m e s
room t e m p e r a t u r e .
a
Without the cooling c o i l ,
below
vapor bubbled t h r o u g h the
r e s i d u e chamber t o o f a s t t o r e a c h e q u i l i b r i u m w i t h t h e l i q u i d p h a s e
t h e r e , a n d c a u s e d s u c h a n o v e r l o a d on t h e f l a s h b o i l e r t h a t
entrainment
resulted.
As t h e w e a t h e r became warm a n d h u m i d , w a t e r c o n d e n s i n g f r o m t h e
air
on t h e c o l d o u t e r s u r f a c e s o f t h e condensers p r e s e n t e d a p r o b l e m .
T h i s w a t e r d r i p p i n g on t h e f l a s h b o i l e r c o m p l e t e l y u p s e t o p e r a t i o n
t h e i n s t r u m e n t , a n d i n d r i p p i n g down t h e d i s t i l l a t e chamber
t u b e , threatened to contaminate samples.
of
delivery
D e v i c e s w e r e made o f
paper
5
i n s u l a t e d w i r e , and o f g l a s s w o o l , t h a t e f f e c t i v e l y c o n t r o l l e d t h i s
water
so t h a t i t d r i p p e d h a r m l e s s l y o n t o s p o n g e s p r o v i d e d f o r
purpose.
T h e s e d e v i c e s a r e n o t shown i n F i g u r e
this
9*
To m i n i m i z e t h e l o s s o f b r o m i n e v a p o r i n t o t h e a t m o s p h e r e ,
two d e l i v e r y
joints,
tubes were equipped w i t h s t a n d a r d t a p e r ground g l a s s
Erlenmeyer
ground glass j o i n t s ,
librium
the
f l a s k s were equipped w i t h c o r r e s p o n d i n g female
and were used t o i n t r o d u c e l i q u i d i n t o the
equi­
still.
A cold trap,
bottle f u l l
shown i n F i g u r e
of dry ice
9* was s u r r o u n d e d b y a
throughout a l l runs.
thermos
This t r a p prevented mois­
t u r e from e n t e r i n g the system, and a l s o prevented t h e h i g h l y c o r r o s i v e
bromine vapor f r o m e n t e r i n g the pressure
tank.
As i n d i c a t e d i n F i g u r e 99 a t w o - w a y s t o p - c o c k o p e n e d t h e
librium s t i l l
to a water
l e a k - p r o o f metal
aspirator,
or to a pressure tank.
t a n k was e q u i p p e d w i t h a 1/6
This
The t a n k a n d c o m p r e s s o r w e r e u s e d t o m a i n t a i n
pressure i n the e q u i l i b r i u m s t i l l at
760
mm.
large
HP c o m p r e s s o r , a n d was
connected t o the g l a s s tube l e a d i n g f r o m the e q u i l i b r i u m s t i l l
rubber tubing.
equi­
A mercury
by heavy
the
manometer,
c o n n e c t e d t o t h e g l a s s t u b e l e a d i n g t o t h e p r e s s u r e t a n k , was u s e d f o r
r e a d i n g gage p r e s s u r e *
A copper-constantan thermocouple, i n s e r t e d i n t o a
w e l l i n t h e r e s i d u e chamber,
tures.
thermocouple
was u s e d t o m e a s u r e e q u i l i b r i u m
tempera­
The c o l d j u n c t i o n was i n a b a t h o f f i n e l y c r u s h e d m e l t i n g
h e l d i n a dewar f l a s k s u r r o u n d e d by a s b e s t o s i n s u l a t i o n .
c o u p l e was c o n n e c t e d t o a L e e d s a n d N o r t h r u p N o .
r e a d i n g t o 0.001
millivolt.
7651
The
ice,
thermo­
potentiometer
T h i s number o f m i l l i v o l t s c o r r e s p o n d s
to
6
about-0.01 degrees c e n t i g r a d e .
Variations i n the potentiometer c i r c u i t
and f l u c t u a t i o n s i n t h e o p e r a t i o n o f t h e s t i l l ,
l i b r i u m t e m p e r a t u r e s a c c u r a t e t o o n l y a b o u t 0.1°
made t h e r e c o r d e d e q u i ­
C
I n r e b u i l d i n g the
a p p a r a t u s f o r t h i s i n v e s t i g a t i o n , i t was n e c e s s a r y t o make a new
copper-constantan thermocouple.
a c o r r e c t e d 100°
x 0.1°
The t h e r m o c o u p l e was c a l i b r a t e d
C, 76 mm i m m e r s i o n
against
thermometer.
A device f o r removing a l l traces of water from the e q u i l i b r i u m
still
i s i n d i c a t e d i n F i g u r e 10.
B|y means o f t h e w a t e r a s p i r a t o r ,
air
was b u b b l e d t h r o u g h c o n c e n t r a t e d s u l f u r i c a c i d , was p a s s e d o v e r
soda-
l i m e , and t h e n i n t o t h e e q u i l i b r i u m s t i l l .
still
When n e c e s s a r y ,
the
was a l s o warmed b y means o f t h e t h r e e h e a t i n g c o i l s a l r e a d y d i s c u s s e d .
The L a r g e F r a c t i o n a t i n g C o l u m n
A f i v e f o o t g l a s s h e l i x p a c k e d c o l u m n was u s e d t o p u r i f y
l,l-dichloro-2,2-difluoroethane
and
l,2,2-trichloro-l,l-difluoroethane.
T h i s c o l u m n was a l s o u s e d t o s e p a r a t e p u r e s o l v e n t f r o m a m i x t u r e
of
b r o m i n e and s o l v e n t , i n t e s t i n g f o r t h e p o s s i b i l i t y o f r e a c t i o n .
The c o l u m n was e q u i p p e d w i t h a h e a t i n g c o i l o f n i c h r o m e w i r e ,
c o n n e c t e d t h r o u g h a G e n e r a l R a d i o Company V a r i a c
voltage transformer.
The d i s t i l l i n g
t o a Sola
constant
f l a s k was h e a t e d b y means o f
G l a s - C o l h e a t i n g m a n t l e , c o n n e c t e d i n t h e same w a y .
a
A n a i r gap i n ­
s u l a t e d the column f r o m the s u r r o u n d i n g atmosphere.
D u r i n g a l l r u n s , a r e f l u x r a t i o o f more t h a n 20-1
a n d i c e w a t e r was c i r c u l a t e d t h r o u g h t h e
was m a i n t a i n e d ,
condenser.
The S m a l l F r a c t i o n a t i n g C o l u m n
T h i s c o l u m n h a s a p a c k e d s e c t i o n a b o u t hp c e n t i m e t e r s l o n g a n d
7
2 centimeters i n diameter,
and i s packed w i t h 3 / l 6
The c o l u m n i s i n s u l a t e d w i t h g l a s s w o o l .
inch glass
helices.
H e a t was a p p l i e d b y a
Glas-Col heating mantle which surrounded the d i s t i l l i n g f l a s k .
column i s equipped w i t h s t a n d a r d t a p e r ground g l a s s j o i n t s f o r
ing flask,
thermometer,
and t a k e - o f f .
The
distill­
A glass tube l e d from the c o n ­
d e n s e r t o a c o l d t r a p w h i c h was s u r r o u n d e d b y d r y i c e d u r i n g a l l r u n s .
During o p e r a t i o n , a rubber tube l e d from the c o l d t r a p mentioned
above,
t o t h e d i s t i l l a t e chamber d e l i v e r y t u b e o f t h e e q u i l i b r i u m s t i l l .
In
t h i s manner t h e p r e s s u r e c o n t r o l a p p a r a t u s d e s c r i b e d a b o v e , c o u l d be
u s e d t o m a i n t a i n a p r e s s u r e o f 760 mm o n t h e c o l u m n .
plained later,
t h i s c o l u m n was u s e d t o p r e p a r e
A s w i l l be
ex­
azeotropes.
A p p a r a t u s f o r M e a s u r i n g Volume Change o n M i x i n g
The a p p a r a t u s f o r m e a s u r i n g v o l u m e c h a n g e on m i x i n g c o n s i s t e d
s i m p l y o f two t e n m i l l i l i t e r b u r e t s , and a small graduated
cylinder.
The g r a d u a t e d c y l i n d e r was made b y s e a l i n g a n d r o u n d i n g t h e t i p o f a
ten m i l l i l i t e r pipet.
The p l p e t was c u t a t t h e f o u r m i l l i l i t e r m a r k ,
a n d a r i n g o f g l a s s b e a d s was a t t a c h e d j u s t b e l o w t h i s m a r k s o
that
t h e c y l i n d e r c o u l d be h u n g .
The c y l i n d e r w a s c a l i b r a t e d f o r r e a d i n g t h e t o p m e n i s c u s ,
by
m e a s u r i n g a number o f s a m p l e s o f p o t a s s i u m p e r m a n g a n a t e s o l u t i o n i n
w a t e r , i n t o t h e c l e a n d r y c y l i n d e r f r o m each o f t h e b u r e t s .
8
Materials
Bromine
!
B a k e r s a n a l y z e d C. P. b r o m i n e was u s e d f o r a l l s y s t e m s .
No
f u r t h e r p u r i f i c a t i o n was p e r f o r m e d .
Solvents
T r i c h l o r o m o n o f l u o r o m e t h a n e . — T h i s s o l v e n t , "Freon 11,
by the " K i n e t i c " Chemicals D i v i s i o n o f E.
I.
n
was c o n t r i b u t e d
d u P o n t de Nemours & C o . .
E x c e p t f o r s t r a i g h t d i s t i l l a t i o n i n a l l g l a s s a p p a r a t u s , no f u r t h e r
p u r i f i c a t i o n was p e r f o r m e d .
l,l-dichloro-2,2-difluoroethane.—This
compound was p u r c h a s e d f r o m
Halogen Chemicals I n c . ,
a n d was s t a t e d b y i t s m a n u f a c t u r e r t o be
t h a n 95 p e r c e n t p u r e .
F u r t h e r p u r i f i c a t i o n was p e r f o r m e d b y f r a c t i o n ­
a l d i s t i l l a t i o n i n the l a r g e r column d e s c r i b e d above.
t h i s d i s t i l l a t i o n w i l l be f o u n d i n T a b l e 2,
An a c c o u n t
a n d i n F i g u r e 3.
c u t c o n s i s t i n g o f f r a c t i o n s f o u r t h r o u g h e i g h t was
b e t t e r t h a n 95 p e r c e n t p u r e .
of
A middle
used.
1 , 2 , 2 - t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e . — T h i s compound was a l s o
from Halogen Chemicals I n c . ,
better
purchased
and was s t a t e d b y i t m a n u f a c t u r e r t o
be
F u r t h e r p u r i f i c a t i o n was p e r f o r m e d b y
f r a c t i o n a l d i s t i l l a t i o n i n the l a r g e r column.
t i o n w i l l be f o u n d i n T a b l e U, a n d i n F i g u r e 6.
i n g o f f r a c t i o n s f o u r t h r o u g h n i n e was u s e d .
Data on t h i s d i s t i l l a ­
A middle cut c o n s i s t ­
CHAPTER
III
PROCEDURE AMD RESULTS
9
CHAPTER
III
PROCEDURE AND RESULTS
General Procedure f o r Operating the E q u i l i b r i u m S t i l l
B e f o r e s t u d y i n g e a c h s y s t e m t h e e q u i l i b r i u m s t i l l was
cleaned, rinsed several
times w i t h d i s t i l l e d water,
thoroughly
rinsed with
t h e n d r i e d b y d r a w i n g a i r f r o m t h e d r y i n g t r a i n o f F i g u r e 10
the apparatus over
through
night.
P u r e s o l v e n t was t h e n i n t r o d u c e d i n t o t h e a p p a r a t u s .
water
heater
c i r c u l a t i n g through the condensers,
o n , an E r l e n m e y e r
With
and o n l y t h e f l a s h
f l a s k f i t t e d w i t h a standard taper
g r o u n d g l a s s j o i n t and c o n t a i n i n g a t l e a s t
tube.
ice
boiler
female
2£ m l o f s o l v e n t , was
l y a t t a c h e d t o t h e d i s t i l l a t e chamber d e l i v e r y
stopcocks were
acetone,
loose­
The d e l i v e r y
c l o s e d a n d t h e a s p i r a t o r was a d j u s t e d so t h a t
tube
the
p r e s s u r e w i t h i n t h e a p p a r a t u s was o n l y s l i g h t l y l e s s t h a n t h a t o f
the
atmosphere.
that
The d i s t i l l a t e chamber s t o p c o c k was s l o w l y o p e n e d so
l i q u i d was d r a w n i n t o t h e d i s t i l l a t e c h a m b e r ,
t h e f l a s h b o i l e r i n t o t h e r e s i d u e chamber.
almost t o the bottom o f the Erlenmeyer
through
The d e l i v e r y t u b e
flask,
o f t h e c o n t e n t s c o u l d be i n t r o d u c e d i n t o t h e
and o v e r f l o w e d
reached
so t h a t v e r y n e a r l y
all
apparatus.
The t w o - w a y s t o p c o c k was t h e n o p e n e d t o t h e p r e s s u r e t a n k w h i c h
had been opened t o t h e atmosphere.
B a r o m e t r i c p r e s s u r e was
determined,
a n d e n o u g h g a g e p r e s s u r e was a p p l i e d t o t h e t a n k t o c o r r e c t t h e
s u r e w i t h i n t h e e q u i l i b r i u m s t i l l t o 760
mm.
pres­
B o t h b a r o m e t r i c a n d gage
10
pressures were
checked s e v e r a l
s u r e o f t h e t a n k changed i f
t i m e s d u r i n g e a c h r u n , a n d t h e gage p r e s ­
necessary.
Once t h e s t i l l h a d b e e n f i l l e d ,
and t h e p r e s s u r e a d j u s t e d ,
i t
was n e c e s s a r y t o r e g u l a t e t h e h e a t s u p p l i e d t o t h e f l a s h b o i l e r ,
residue
chamber,
vapor
and v a p o r l i n e *
The r e g u l a t i o n o f h e a t s u p p l i e d t o t h e
l i n e was n o t s e n s i t i v e , f o r i t w a s o n l y r e q u i r e d t h a t t h e
o f t h e v a p o r l i n e be g r e a t e r
temperature
t h a n t h a t o f t h e r e s i d u e chamber.
This
p r e c a u t i o n p r e v e n t e d vapor f r o m condensing back i n t o the l i q u i d phase,
and p r e v e n t e d r e f l u x i n g and t h e r e f o r e f r a c t i o n a t i o n .
The
flash boiler
t e m p e r a t u r e w a s a d j u s t e d so t h a t a s t e a d y s t r e a m o f v a p o r b u b b l e d a r o u n d
the thermocouple w e l l .
great,
I f t h i s s t r e a m o f b u b b l e s was n o t s u f f i c i e n t l y
t h e l i q u i d i n t h e r e s i d u e chamber was n o t m a i n t a i n e d a t
equilib­
r i u m t e m p e r a t u r e , a n d t h e t e m p e r a t u r e r e a d was v e r y s e n s i t i v e t o
s l i g h t c h a n g e s i n t h e a d j u s t m e n t o f t h e r e s i d u e chamber h e a t i n g
On t h e o t h e r h a n d , i f t o o much h e a t was s u p p l i e d t o t h e f l a s h
very
coil.
boiler,
v a p o r b u b b l e d t h r o u g h t h e r e s i d u e chamber t o o r a p i d l y t o a t t a i n e q u i l i b ­
rium.
The m o s t s e n s i t i v e a d j u s t m e n t was t h a t o f t h e h e a t s u p p l i e d t o
t h e r e s i d u e chamber.
If
i n s u f f i c i e n t h e a t was s u p p l i e d , v a p o r
t h e f l a s h b o i l e r w o u l d c o n d e n s e i n t h e r e s i d u e chamber a n d
would cease.
If
leaving
operation
t o o much h e a t was s u p p l i e d , t h e f l a s h b o i l e r w o u l d be
o v e r l o a d e d and l i q u i d c o l l e c t i n g t h e r e w o u l d be e n t r a i n e d w i t h v a p o r
i n t o t h e r e s i d u e chamber.
T h i s a d j u s t m e n t was d e p e n d e n t o n t h e
heat
s u p p l i e d t o t h e H a s h b o i l e r , f o r a r a p i d stream o f vapor passing through
t h e r e s i d u e chamber b r o u g h t i n more h e a t e n e r g y t h a n d i d a s l o w s t r e a m .
To a l e s s e r ,
but noticeable extent,
t h i s a d j u s t m e n t was a l s o
dependent
11
on t h e r a t e o f c i r c u l a t i o n o f condenser c o o l i n g w a t e r .
The h e a t
t o t h e r e s i d u e chamber was s o a d j u s t e d t h a t l i q u i d was a t a l l
supplied
times
m a i n t a i n e d a t t h e b o t t o m o f t h e f l a s h b o i l e r , so t h a t s u p e r h e a t i n g
the flash b o i l e r could not occur.
this liquid at
T h i s h e a t was a l s o s o a d j u s t e d
in
that
the b o t t o m o f t h e f l a s h b o i l e r d i d n o t i n c r e a s e i n volume
enough t o be e n t r a i n e d i n t o the r e s i d u e chamber.
t i o n s had been f u l f i l l e d ,
When a l l t h e s e c o n d i ­
i t was f e l t t h a t t h e t e m p e r a t u r e r e a d was
true e q u i l i b r i u m temperature.
I t was o b s e r v e d e x p e r i m e n t a l l y ,
l i q u i d d i d not q u i t e reach the bottom o f the f l a s h b o i l e r the
the
that
if
temperature
r e a d i n g was l o w , a n d t h a t i f a p o o l o f l i q u i d c o l l e c t e d a t t h e b o t t o m o f
t h e f l a s h b o i l e r t h e t e m p e r a t u r e r e a d i n g was h i g h .
When t h e s e c o n d i t i o n s h a d b e e n m a i n t a i n e d s u f f i c i e n t l y l o n g f o r
e q u i l i b r i u m t o b e r e a c h e d , t h e t e m p e r a t u r e was d e t e r m i n e d b y means
the thermocouple and p o t e n t i o m e t e r a l r e a d y d e s c r i b e d .
were
of
Several readings
t a k e n o v e r a p e r i o d o f a t l e a s t h a l f a n h o u r t o be s u r e t h a t
equi­
l i b r i u m had been r e a c h e d .
After
thus o b t a i n i n g t h e b o i l i n g p o i n t o f pure s o l v e n t , r u n s were
made w i t h s o l u t i o n s o f t h e s o l v e n t a n d b r o m i n e r a n g i n g f r o m 0 p e r
t o 100 p e r c e n t b r o m i n e .
Between e a c h o f t h e s e r u n s , t h e e q u i l i b r i u m
s t i l l was d r i e d b y p a s s i n g a i r
the s t i l l
over n i g h t .
cent
f r o m t h e d r y i n g t r a i n o f F i g u r e 10
The p r o c e d u r e o f i n t r o d u c i n g s o l u t i o n s a n d
through
deter­
m i n i n g t h e i r e q u i l i b r i u m t e m p e r a t u r e s was i d e n t i c a l t o t h a t g i v e n a b o v e
f o r pure s o l v e n t .
S i n c e v a p o r and l i q u i d phases d i f f e r e d g r e a t l y
in
c o m p o s i t i o n f o r e a c h o f t h e s e s o l u t i o n s , h o w e v e r , a b o u t a n h o u r was
a l l o w e d f o r e q u i l i b r i u m t o be r e a c h e d .
The p r o c e d u r e f o l l o w e d i n
i n g t h e l i q u i d a n d v a p o r p h a s e s o f t h e s e s o l u t i o n s w i l l be
analyz­
presented
12
below.
G e n e r a l Method o f A n a l y s i s
Because o f t h e v o l a t i l i t y o f t h e l i q u i d s ,
ground-glass stoppered weighing b o t t l e s .
o f a p p r o x i m a t e l y 50
t h e y were weighed
in
A number o f w e i g h i n g b o t t l e s
m l c a p a c i t y a n d a b o u t h$ grams i n w e i g h t w e r e u s e d .
The t w o b o t t l e s h a v i n g t h e l e a s t w e i g h t w e r e m a r k e d a n d e a c h was u s e d a s
a counterpoise.
I n p r e p a r a t i o n f o r e a c h r u n , 20 m l o f a s o l u t i o n o f
p o t a s s i u m i o d i d e , s o made u p t h a t e a c h
20
ml contained
3.072
grams
p o t a s s i u m i o d i d e , was p o u r e d i n t o e a c h o f e i g h t o f t h e s e b o t t l e s .
of
The
b o t t l e s w e r e p l a c e d i n a s h a l l o w , h a r d r u b b e r p a n , a n d c r u s h e d i c e was
p a c k e d a r o u n d t h e m s o t h a t t h e i c e d i d n o t e x t e n d much a b o v e t h e
liquid
l e v e l i n s i d e of the b o t t l e s .
From t h e m a t e r i a l a l r e a d y p r e s e n t e d , i t
has p r o b a b l y been
e d t h a t t h e l i q u i d i n t h e d i s t i l l a t e chamber i s c o n d e n s e d v a p o r
gather­
phase,
and t h a t v a p o r o f t h i s c o m p o s i t i o n i s i n e q u i l i b r i u m w i t h t h e l i q u i d
phase w h i c h i s i n t h e r e s i d u e chamber.
The s m a l l amount o f l i q u i d i n
e a c h chamber w h i c h m i g h t h a v e r e m a i n e d s t a g n a n t d u r i n g t h e r u n was
withdrawn.
The r e s i d u e chamber a n d v a p o r l i n e h e a t i n g c o i l s w e r e
im­
mediately c u t o f f t o prevent f u r t h e r evaporation o f the l i q u i d phase.
The f l a s h b o i l e r h e a t i n g c o i l was l e f t o n t o p r e v e n t l i q u i d f r o m b e i n g
drawn i n t o t h e f l a s h b o i l e r f r o m t h e r e s i d u e
chamber.
One o f t h e p r e p a r e d b o t t l e s m a r k e d f o r u s e a s a c o u n t e r p o i s e ,
and
a s e c o n d b o t t l e was removed f r o m t h e c r u s h e d i c e m e n t i o n e d a b o v e .
The
b o t t l e s w e r e c h e c k e d t o i n s u r e t h a t n o m o i s t u r e was p r e s e n t on t h e
ground
g l a s s o f t h e i r n e c k s , d i p p e d i n a c e t o n e t o remove t r a c e s o f w a t e r ,
dried
13
w i t h clean paper
t o w e l s and w e i g h e d .
The c o u n t e r p o i s e was p l a c e d o n t h e
r i g h t hand balance d u r i n g w e i g h i n g , and r e c o r d i n g o f t h e l a s t two
sig­
n i f i c a n t f i g u r e s was d e l a y e d u n t i l t h e c o l d w e i g h i n g b o t t l e s r e a c h e d
stable weight.
Beakers
o f d r y s i l i c a g e l placed i n the balance
a
case
seemed t o make t h e a m o u n t o f m o i s t u r e c o n d e n s i n g on t h e b o t t l e s
slightly
less.
A f e w d r o p s o f l i q u i d f r o m t h e d i s t i l l a t e chamber d e l i v e r y
were t h e n q u i c k l y i n t r o d u c e d i n t o the second w e i g h i n g b o t t l e ,
the t i p o f the d e l i v e r y tube close t o the surface of the
iodide
solution.
tube
holding
potassium
T h i s b o t t l e was t h e n q u i c k l y r e w e i g h e d , u s i n g t h e
c o u n t e r p o i s e as b e f o r e .
C a r e was t a k e n t o h a n d l e
a n d c o u n t e r p o i s e i n j u s t t h e same w a y .
w i t h approximately 0.2
N standardized
the weighing
bottle
The l i b e r a t e d i o d i n e was
titrated
sodium t h i o s u l f a t e s o l u t i o n t o
a
s t a r c h i n d i c a t o r end p o i n t .
The c o u n t e r p o i s e j u s t u s e d was r e t u r n e d t o t h e p a n o f c r u s h e d
f o r l a t e r use.
A s e c o n d c o u n t e r p o i s e and a n o t h e r
of the
prepared
w e i g h i n g b o t t l e s was u s e d t o a n a l y z e t h e
contents of the residue
f o l l o w i n g the procedure o u t l i n e d above.
T h i s p r o c e d u r e was
u n t i l t h r e e samples had been a n a l y z e d
m e n t was g e n e r a l l y q u i t e
ice
chamber,
followed
from each o f the chambers.
good, and t h e average a n a l y s i s o f t h e
Agree­
samples
was t a k e n as t h e c o n c e n t r a t i o n o f e a c h p h a s e .
The s o d i u m t h i o s u l f a t e s o l u t i o n s w e r e s t a b a l i z e d b y t h e
of 0.1
gram s o d i u m c a r b o n a t e p e r l i t e r o f s o l u t i o n . * ^
addition
These s o l u t i o n s w e r e
standardized by t i t r a t i o n a g a i n s t 0.2000 N potassium dichromate
solution,
7
'Rieman, Neuss, and Naiman, Q u a n t i t a t i v e A n a l y s i s , Second e d i t i o n ,
(New Y o r k a n d L o n d o n : M c G r a w - H i l l Book Company I n c . , I ? i i 2 ) , p . 2 2 1 .
11*
prepared by d i r e c t w e i g h i n g .
i o d i d e as a p r e s e r v a t i v e ,
and S a n d e H ,
0
Starch solutions contained
mercuric
a n d w e r e made u p b y t h e d i r e c t i o n s o f
e x c e p t t h a t p o t a t o s t a r c h was u s e d . 2
Kolthoff
The p r o c e d u r e u s e d
in
s t a n d a r d i z i n g sodium t h i o s u l f a t e s o l u t i o n s a g a i n s t potassium dichromate
s o l u t i o n was a d a p t e d f r o m t h e p r o c e d u r e g i v e n i n K o l t h o f f a n d
Sandell.
1 0
P r a c t i c a l l y n o change o c c u r r e d i n t h e s t a n d a r d o f t h e s o d i u m t h i o s u l f a t e
s o l u t i o n s i n t h e t i m e r e q u i r e d f o r t h e i r c o n s u m p t i o n , as v e r i f i e d
frequent
checks.
The S y s t e m
Operation
this
Bromine-Trichloromonofluoromethane
of the Equilibrium S t i l l . — B e c a u s e
o f the low b o i l i n g p o i n t
s y s t e m a number o f d i f f i c u l t i e s w e r e e n c o u n t e r e d .
p l a i n e d p r e v i o u s l y , i t was n e c e s s a r y
residue
by
chamber,
As has been
s t i l l c o u l d be c o n t r o l l e d .
ex­
to construct a cooling c o i l for
i n order t h a t the heat applied t o t h i s p o r t i o n o f
I t was a l s o d e s i r a b l e
that the
of
the
the
condensed
v a p o r i n t h e d i s t i l l a t e chamber be k e p t w e l l b e l o w i t s b o i l i n g p o i n t .
Much o f t h e w o r k o n t h i s s y s t e m was done i n c o l d w e a t h e r ,
t o r y windows were opened t o keep t h e room t e m p e r a t u r e
and t h e
low.
I n i n t r o d u c i n g s o l v e n t - r i c h solutions i n t o the s t i l l ,
t o be t a k e n t o p r e v e n t the l i q u i d f r o m suddenly b o i l i n g and
l i q u i d i n t o the c o l d t r a p .
c a r e was t a k e n t o d e c r e a s e
cause l i q u i d t o be d r a w n
care
O n l y c o l d s o l u t i o n s were so i n t r o d u c e d ,
the pressure w i t h i n the s t i l l
o n l y enough
in.
K o l t h o f f and S a n d e l l , Textbook o f Q u a n t i t a t i v e
(New X o r k r
The M a c i t t l l a n C o . ,
p . 607H
1
1 0
p.
6 1 9 .
Ibid.,
p.
62k.
had
entraining
Q
%bid.,
labora­
9
U
7
)
,
Analysis.
and
to
15
A t h i n f i l m o f D o w - C o r n i n g s i l i c o n e s t o p c o c k g r e a s e was u s e d o n
the stopcocks i n studying t h i s system.
Method o f A n a l y s i s . — T h e
g e n e r a l method o f a n a l y s i s a l r e a d y
was e v o l v e d t o d e a l w i t h t h e h i g h v o l a t i l i t y o f
presented
this solvent.
At
first,
t h e w e i g h i n g b o t t l e s o f p o t a s s i u m i o d i d e s o l u t i o n were c o o l e d i n d r y
u n t i l c r y s t a l s began t o f o r m .
T h i s p r o v e d t o be i m p r a c t i c a l ,
f o r m o i s t u r e c o n d e n s a t i o n on t h e s u r f a c e
however,
o f t h e w e i g h i n g b o t t l e s was
s o g r e a t a s t o make w e i g h i n g s l e s s e x a c t .
A l s o , t h e c r y s t a l s so
h a d t o be m e l t e d b e f o r e t i t r a t i o n c o u l d be c o m p l e t e d .
ed i s i d e n t i c a l t o t h a t a l r e a d y p r e s e n t e d ,
studied.
formed
The m e t h o d f o l l o w ­
except that the
weighing
b o t t l e s w e r e k e p t somewhat c o l d e r t h a n t h e y w e r e when t h e o t h e r
were
systems
I t was e s p e c i a l l y t r u e i n s t u d y i n g t h i s s y s t e m t h a t
b o t t l e s had t o be w e i g h e d q u i c k l y a f t e r
ice
the
i n t r o d u c i n g samples i n t o
them.
As a f u r t h e r p r e c a u t i o n , t h e b o t t l e s w e r e a g a i n p l u n g e d i n t o i c e
after
b e i n g w e i g h e d , and were
k e p t t h e r e u n t i l t h e s a m p l e s c o u l d be
l e s s than a minute l a t e r .
titrated
Agreement between s e v e r a l a n a l y s e s
were
u s u a l l y f a i r l y g o o d t o t h e t h i r d d e c i m a l , as e x p r e s s e d i n m o l e f r a c t i o n s .
Results from F r a c t i o n a t i n g Column.—Data
still
i n d i c a t e s t h a t no a z e o t r o p e
assurance
t h a t no a z e o t r o p e
obtained from the
equilibrium
i s formed i n t h i s system.
i s f o r m e d a t 760
As a
mm p r e s s u r e n e a r
the
s o l v e n t - r i c h end o f t h i s system, s o l u t i o n s r i c h i n s o l v e n t were
ated.
The s m a l l f r a c t i o n a t i n g c o l u m n was u s e d a t
mm.
final
fraction­
total reflux,
and
p r e s s u r e o n t h e c o l u m n was m a i n t a i n e d a t
760
Only a few drops
d i s t i l l a t e were w i t h d r a w n f o r a n a l y s i s .
The a n a l y t i c a l p r o c e d u r e
i d e n t i c a l t o t h a t used i n a n a l y z i n g samples f r o m t h e e q u i l i b r i u m
of
was
still.
16
Three samples were a n a l y z e d and t h e r e s u l t s a v e r a g e d .
two f r a c t i o n a t i o n s performed are presented i n Table 1 .
rather poorly insulated.
Ihen the f i r s t
Results of
T h i s column i s
s o l u t i o n was f r a c t i o n a t e d ,
r o o m t e m p e r a t u r e was a b o u t f i v e d e g r e e s a b o v e t h e c o r r e c t e d
r e a d on t h e c o l u m n t h e r m o m e t e r .
the
temperature
TShen t h e 0 . 0 l * ° m o l e f r a c t i o n s o l u t i o n
was f r a c t i o n a t e d , r o o m t e m p e r a t u r e was a b o u t t w o d e g r e e s b e l o w t h e
c o r r e c t e d t e m p e r a t u r e r e a d on t h e column thermometer.
V o l u m e Change o n M i x i n g * — M e a s u r e m e n t
o f t h e v o l u m e change o c c u r r i n g o n
m i x i n g t r i c h l o r o m o n o f l u o r o m e t h a n e and b r o m i n e was n o t a t t e m p t e d ,
t h e b o i l i n g p o i n t o f t h e s o l v e n t was b e l o w r o o m t e m p e r a t u r e .
because
Large
c h a n g e s i n t e m p e r a t u r e d u r i n g m e a s u r e m e n t c o u l d n o t be p e r m i t t e d ,
for
t h e e f f e c t o f s u c h c h a n g e s on v o l u m e w o u l d r e n d e r a n y r e s u l t s m e a n i n g ­
less.
I t w o u l d be n e c e s s a r y ,
t h e r e f o r e , t o c a r r y o u t s u c h measurements
a t the temperature
o f the surroundings.
available,
of the c o r r o s i v e nature o f bromine.
because
A i r c o n d i t i o n i n g w a s n o t made
The S y s t e m B r o m i n e - l , l - d i c h l o r o - 2 , 2 - d i f l u o r o e t h a n e
Operation of the E q u i l i b r i u m S t i l l . — S i n c e the s o l v e n t used i n
s y s t e m b o i l e d w e l l above r o o m t e m p e r a t u r e ,
this
and b e c a u s e e q u i l i b r i u m t e m ­
p e r a t u r e s over the e n t i r e system v a r i e d t h r o u g h a small
r a n g e , no s p e c i a l d i f f i c u l t i e s were e n c o u n t e r e d .
temperature
The p r o c e d u r e
followed
i s t h a t presented under General Procedure f o r Operating the E q u i l i b r i u m
Still.
D o w - C o r n i n g s i l i c o n e s t o p c o c k g r e a s e was s p a r i n g l y u s e d .
Method o f A n a l y s i s . — T h e method o f a n a l y s i s f o l l o w e d f o r t h i s system i s
i d e n t i c a l t o t h a t p r e s e n t e d u n d e r G e n e r a l Method o f A n a l y s i s .
17
Results f r o m t h e Small F r a c t i o n a t i n g Column.—From
from the equilibrium s t i l l ,
gram, t h e approximate
interpolation.
obtained
p l o t t e d on a v a p o r - l i q u i d e q u i l i b r i u m
composition o f t h e azeotrope
A mixture o f very nearly
r i c a l l y prepared,
the data
was o b t a i n e d b y
t h i s c o m p o s i t i o n was v o l u m e t -
a n d f r a c t i o n a t e d a t a p r e s s u r e o f 760 mm.
was c i r c u l a t e d t h r o u g h t h e c o n d e n s e r .
I c e water
After leaving the s t i l l a t
r e f l u x f o r some t i m e , a s m a l l q u a n t i t y o f d i s t i l l a t e was s l o w l y
o f f a t a r i g h r e f l u x r a t i o u n t i l t h e temperature
discarded.
M o r e t h a n 25 m l o f a z e o t r o p e
samples were a n a l y z e d
at intervals.
dia­
total
drawn
became c o n s t a n t , a n d
was t h e n s l o w l y c o l l e c t e d , a n d
Before t a k i n g each sample, t h e
c o l u m n was r u n f o r a f e w m i n u t e s a t t o t a l r e f l u x a n d t h e p r e s s u r e was
checked.
The column t e m p e r a t u r e
azeotrope
were
i s recorded
collected.
i n T a b l e 3.
remained
c o n s t a n t w h i l e t h e 25 m l o f
Three samples were a n a l y z e d
The r e a d i n g
and t h e i r
average
o f t h e column thermometer was
c o r r e c t e d t o 1*9 • 5° C .
As a n a d d i t i o n a l c h e c k ,
the d i s t i l l a t e c o l l e c t e d from the small
fractionating column as j u s t described,
rium s t i l l .
The
boiling
was i n t r o d u c e d i n t o t h e e q u i l i b ­
p o i n t o f the azeotrope
m i n e d by means o f t h e r m o c o u p l e
readings.
t h a t t h e b o i l i n g p o i n t i s nearer
1.9.6°
Test f o r P o s s i b i l i t y o f Reaction.—As
these
e d , however,
C than
The r e f r a c t i v e
1.9.5°
i t
deter­
appears
C.
mentioned i n t h e i n t r o d u c t i o n , t h e
c o n d i t i o n s , d i d n o t seem g r e a t .
by the following
760 mm was t h e n
From t h e s e r e a d i n g s ,
p o s s i b i l i t y t h a t bromine would r e a c t w i t h
under
at
l,l-dichloro-2,2-difluoroethane
T h i s p o s s i b i l i t y was c h e c k ­
procedure.
i n d e x o f f r a c t i o n number 8, f r o m t h e p u r i f i c a t i o n
18
of this solvent
( s e e T a b l e 2 a n d F i g u r e 3) w a s m e a s u r e d a t 25°
C and
f o u n d t o be 1.3769.
A s o l u t i o n c o n s i s t i n g o f 10 p e r c e n t b r o m i n e i n f r a c t i o n number
8,
was v o l u m e t r i c a l l y p r e p a r e d a n d f r a c t i o n a l l y d i s t i l l e d i n t h e l a r g e
f i v e - f o o t column.
the residue.
The a z e o t r o p e
The r e f r a c t i v e
d i s t i l l e d over l e a v i n g c l e a r
indices after
s o l v e n t as
c o n t a c t were d e t e r m i n e d
from
samples o f l i q u i d t h a t condensed f r o m t h e b o t t o m o f t h e f r a c t i o n a t i n g
column.
The f i r s t l i q u i d t o c o n d e n s e a f t e r r e m o v i n g t h e d i s t i l l i n g
f l a s k and r e p l a c i n g i t w i t h a c l e a n f l a s k ,
had a r e f r a c t i v e
i n d e x o f 1.3785*
i s sample # 1 o f T a b l e 6 , a n d
The s e c o n d s a m p l e w h i c h
i n t o another clean f l a s k had a r e f r a c t i v e
i n d e x o f 1.3773.
condensed
I t
appears
t o f o l l o w f r o m a s t u d y o f F i g u r e 3 t h a t a t h i r d sample s h o u l d approach
t h e v a l u e 1.3769 e v e n more c l o s e l y , b u t n o s u c h sample
because o f h o l d u p b y t h e c o l u m n .
could be obtained
A t t h e end o f t h e d i s t i l l a t i o n t h e
d i s t i l l i n g f l a s k was d r y a n d c o n t a i n e d a speck o f c h a r r e d
solvent.
D i s t i l l a t e f r o m t h e t o p o f t h e column s t i l l c o n t a i n e d t r a c e s o f bromine
as i n d i c a t e d b y t h e e f f e c t
solution.
o f a f e w d r o p s on a s t a r c h - p o t a s s i u m
iodide
L i q u i d condensing f r o m t h e b o t t o m o f t h e column (samples
a n d #2 a b o v e )
was f r e e
Incidental
o f bromine by t h i s
#1
test.
t o t h i s t e s t f o r r e a c t i o n , t h r e e samples o f t h e f i r s t
f e w m i l l i l i t e r s o f d i s t i l l a t e were a n a l y z e d and f o u n d t o have a c o m p o s i ­
t i o n o f 0.568 m o l e f r a c t i o n b r o m i n e .
Atmospheric pressure a few hours
b e f o r e m a k i n g t h i s a n a l y s i s was 730*9 mm. T h i s v a l u e t h e n , s h o u l d be
a good e s t i m a t e
o f t h e composition o f the azeotrope
a t 731 mm p r e s s u r e .
formed by t h i s
system
19
V o l u m e Change on M i x i n g , — T h e
for
this determination.
ing,
a p p a r a t u s p r e v i o u s l y d e s c r i b e d was
C a r e was t a k e n t o a v o i d m e c h a n i c a l l o s s o n m i x ­
a n d t h e g r a d u a t e d c y l i n d e r was q u i c k l y s t o p p e r e d a f t e r b e i n g
The v o l u m e o f t h e m i x t u r e was r e a d a f t e r
cooling effect.
filled.
several intervals of time,
assure t h a t the m i x t u r e had r e t u r n e d t o room temperature
after
the
to
initial
The q u a n t i t i e s o f s o l v e n t a n d b r o m i n e i n t r o d u c e d i n t o
the c y l i n d e r were
such t h a t t h e r e s u l t i n g m i x t u r e had a p p r o x i m a t e l y
composition o f the azeotrope.
for
used
The p e r c e n t i n c r e a s e
t h i s s y s t e m w a s f o u n d t o be 1.8.
Measurements
the
i n v o l u m e on m i x i n g
w e r e made t o
three
s i g n i f i c a n t f i g u r e s , b u t due t o l o s s b y e v a p o r a t i o n , p r e c i s i o n
beyond
t w o s i g n i f i c a n t f i g u r e s was n o t o b t a i n e d .
repeated
T h i s e x p e r i m e n t was
s e v e r a l t i m e s and the i n d i v i d u a l r e s u l t s were averaged.
t h i s d e t e r m i n a t i o n are recorded i n Table
The S y s t e m B r o m i n e -
The d a t a
7.
l,2,2-trichloro-l,l-difluoroethane
Operation o f the E q u i l i b r i u m S t i l l . — T h e
procedure followed i s
that
presented under General Procedure f o r Operating the E q u i l i b r i u m
with
the e x c e p t i o n t h a t Dow-Corning s i l i c o n e stopcock grease
be u s e d .
tions.
for
could not
T h i s g r e a s e was d i s s o l v e d b y b o t h p u r e s o l v e n t a n d i t s
A f t e r making the f i r s t
c o c k s was f o u n d d e p o s i t e d a t
Still,
e x p e r i m e n t a l r u n , grease f r o m t h e
the lower end o f the f l a s h b o i l e r .
solu­
stop­
The
s o l u t i o n u s e d was d i s c a r d e d , a n d t h e s t i l l was c l e a n e d w i t h a p o t a s s i u m
hydroxide-ethanol solution.
no l u b r i c a n t .
Since
Thereafter,
n o - l u b s t o p c o c k s were used w i t h
t h e s t i l l was o p e r a t e d u n d e r a b o u t 20 mm p r e s s u r e ,
t h e s e cocks l e a k e d v e r y s l o w l y b u t c o n t i n u o u s l y t h r o u g h o u t each o f
the
runs.
be-
The r e s u l t i n g p r e s s u r e d r o p w i t h i n t h e s t i l l was n e g l i g i b l e
20
cause o f t h e l a r g e
capacity of the pressure tank,
a d j u s t m e n t s w e r e made t o c o m p e n s a t e
and because
frequent
f o r changes i n a t m o s p h e r i c
pressure.
I n m a k i n g t h e s e r u n s i t was n e c e s s a r y t o i n t r o d u c e s l i g h t l y more
t h e u s u a l amount o f s o l u t i o n i n t o t h e e q u i l i b r i u m s t i l l .
After
than
equilib­
r i u m h a d b e e n e s t a b l i s h e d , a n y e x c e s s was w i t h d r a w n t o a d j u s t t h e
l e v e l i n t h e r e s i d u e chamber t o t h a t l e v e l u s e d i n s t u d y i n g t h e
two
liquid
other
systems.
No d i s a d v a n t a g e s r e s u l t e d f r o m t h i s d i f f i c u l t y , e x c e p t
and danger t o t h e o p e r a t o r .
Ammonium h y d r o x i d e was p l a c e d a
distance from the d e l i v e r y tubes to n e u t r a l i z e
vapor w i t h o u t contaminating the
Results
the escaping
gram, t h e approximate
interpolation.
c o m p o s i t i o n o f t h e a z e o t r o p e was o b t a i n e d
a n d f r a c t i o n a t e d a t a p r e s s u r e o f 760
mm.
by
volumetIce
water
A f t e r d i s c a r d i n g the f i r s t
o f d i s t i l l a t e , more t h a n 30 m l o f a z e o t r o p e w a s
c o l l e c t e d , and samples were a n a l y z e d a t i n t e r v a l s .
t h e c o l u m n was r u n f o r a f e w m i n u t e s a t
p r e s s u r e was
obtained
p l o t t e d on a v a p o r - l i q u i d e q u i l i b r i u m d i a ­
was c i r c u l a t e d t h r o u g h t h e c o n d e n s e r .
sample,
bromine
A m i x t u r e o f v e r y n e a r l y t h i s c o m p o s i t i o n was
r i c a l l y prepared,
milliliters
considerable
tubes.
from the Small F r a c t i o n a t i n g Column.—From the data
from the e q u i l i b r i u m s t i l l ,
discomfort
few
slowly
Before t a k i n g each
t o t a l r e f l u x , and
the
checked.
A h e a v y vacuum l u b r i c a n t was a p p l i e d t o t h e u p p e r m o s t p o r t i o n
the standard taper,
male,
ground-glass j o i n t at the bottom o f the
before attaching the d i s t i l l i n g f l a s k .
I t was h o p e d t h a t v a p o r
n o t d i f f u s e t h r o u g h the l o w e r p o r t i o n o f t h e j o i n t , t o such an
column
would
extent
t h a t t h e l u b r i c a n t w o u l d be d i s s o l v e d b e f o r e d i s t i l l a t i o n c o u l d be
of
21
completed.
Such, however, was not the case.
After analyzing two
samples, i t was necessary t o disconnect the heating mantel, because of
bromine vapor escaping into the room.
Apiezon sealing wax was l i b e r a l l y
applied around the j o i n t , and d i s t i l l a t i o n was continued.
samples were analyzed.
Two more
The results o f the best three analyses were
averaged and found to be 0.7U7 mole fraction bromine.
Throughout the c o l l e c t i o n of the more than 30 ml o f azeotrope,
the column temperature remained constant.
As a further check, the
azeotrope was introduced into the equilibrium s t i l l , and i t s boiling
point was determined by thermocouple readings.
The corrected reading of
the column thermometer, and the temperature reading obtained from the
thermocouple agreed within a tenth of a degree.
The boiling point o b ­
tained, 5U.6° C, i s recorded in Table f>.
Test for P o s s i b i l i t y o f Reaction.*—The refractive index of the mixture
of fractions k through 9 from the purification o f this compound (see
Table k and Figure 6) was measured at 25° C, and found to be 1.3900.
This mixture of fractions was used in making solutions for a l l runs made
with this system.
A solution consisting of 10 per cent bromine in the solvent was
volumetrically prepared and fractionally d i s t i l l e d in the large f i v e f o o t column.
The azeotrope d i s t i l l e d over leaving solvent as the residue.
The refractive indices after contact were determined from samples of
liquid that condensed from the bottom o f the fractionating column.
The
f i r s t liquid t o condense after removing the d i s t i l l i n g flask and replac­
ing i t with a clean flask, gave a negative bromine t e s t and had a r e ­
fractive index o f 1.3891.
A second sample obtained in l i k e manner also
22
gave a n e g a t i v e
bromine t e s t ,
The d i s t i l l i n g f l a s k
m i g h t be m e n t i o n e d h e r e ,
and had a r e f r a c t i v e
contained pale
that
1.3899.
index o f
amber c o l o r e d l i q u i d .
It
t h e o r i g i n a l l i q u i d as o b t a i n e d f r o m
manufacturer
was amber c o l o r e d b e f o r e i t was f r a c t i o n a t e d a s
i n T a b l e U.
The f i r s t i n d i c a t i o n t h a t t h i s s o l v e n t w o u l d d i s s o l v e
Corning stopcock grease,
the
indicated
Dow-
was d i s c o v e r e d when a f e w d r o p s o f l i q u i d f r o m
the d i s t i l l i n g f l a s k were dropped i n t o a potassium i o d i d e - s t a r c h
solu­
tion.
sus­
The s t o p c o c k g r e a s e
f l o a t e d t o the l i q u i d surface.
pected t h a t most o f t h i s grease
It
is
got i n t o the d i s t i l l i n g f l a s k a f t e r
was r e m o v e d f r o m t h e c o l u m n a n d c o v e r e d w i t h a b e a k e r .
d e n s i n g on t h e b e a k e r
r a n over the greased,
thus i n t o the f l a s k .
I t was e v i d e n t
Hot vapor
i t
con­
ground-glass
joint,
and
from the appearance
of the
grease
f i l m t h a t much o f i t h a d d i s s o l v e d .
The s a m p l e s c o l l e c t e d f r o m t h e b o t t o m o f t h e c o l u m n f o r
t e s t showed n o i n d i c a t i o n o f t h i s amber c o l o r , a n d w e r e
of stopcock
p r e c e d i n g s y s t e m , so t h a t
measurements
m i x t u r e w o u l d have r o u g h l y t h e
m i x e d , were chosen so t h a t
free
The p e r c e n t i n c r e a s e
d e c i m a l , a n d was f o u n d t o be 0 . 3 .
recorded i n Table
7»
the
in
of
this
t o the t h i r d
averaged.
decimal
t o be due t o c h a n c e r a t h e r
than
i n v o l u m e was r o u n d e d o f f t o t h e
The d a t a
the
resulting
four times, a i d the r e s u l t s
Three o f the i n d i v i d u a l r e s u l t s were i n agreement
but t h i s precision i s believed
as i n
The v o l u m e s
composition o f the azeotrope
The e x p e r i m e n t was r e p e a t e d
accuracy.
apparently
w e r e made e x a c t l y
t h e t w o w o u l d be c o m p a r a b l e .
bromine and s o l v e n t t h a t were
place,
above
grease.
Volume Change o n M i x i n g . — T h e s e
system.
the
for t h i s determination
first
are
CHAPTER IV
DISCUSSION OF RESULTS
23
CHAPTER IV
DISCUSSION OF RESULTS
The System Bromlne-Trichloromonofluoromethane.—Figure 1 i s a p l o t of
the equilibrium temperature v s . mole fraction bromine.
The lower curve
gives the composition of liquid that has atmospheric boiling points
corresponding to points on the ordinate.
The upper curve gives the
composition of vapor that i s in equilibrium with any liquid at i t s b o i l ing point.
I t can be seem from this curve that the boiling point i n ­
creases regularly as the mole fraction of bromine in the liquid is i n ­
creased.
No azeotrope i s formed.
Figure 2 i s a p l o t of mole fraction bromine in the vapor v s .
mole fraction bromine in the l i q u i d .
The almost asymptotic approach of
this curve to the diagonal i s interesting.
From the literature i t was
found that the vapor-liquid equilibrium diagram of the system ethyl
alcohol-water has a very similar shape.
In Chapter I I I , i t was mentioned that solutions r i c h in solvent
were fractionated t o assure the absence of an azeotrope in this system.
Theoretically, any mixture of two liquids showing a regular increase in
boiling point, can be separated into i t s components by fractional
distillation.
The data presented in Table 1, however, indicates that
complete separation was not achieved, when solvent-rich mixtures were
fractionated at total r e f l u x in the small fractionating column.
This disappointing result should not be construed to indicate
azeotrope formation, however, as w i l l be explained.
The f i r s t liquid
2U
f r a c t i o n a t e d was p r e v i o u s l y s e p a r a t e d
v a p o r t h a t was 0.2
i n the equilibrium s t i l l
into
m o l e f r a c t i o n b r o m i n e a n d l i q u i d t h a t was O.h
mole
f r a c t i o n b r o m i n e , a n d i s t h u s j u d g e d t o have an o v e r - a l l c o m p o s i t i o n o f
a b o u t 0.3
mole f r a c t i o n .
t i l l a t e t h a t was
no azeotrope
0.06H
When f r a c t i o n a t e d , t h i s l i q u i d p r o d u c e d
mole f r a c t i o n b r o m i n e .
e x i s t s between about
Fractionation of the
0.0H9
proved t h a t no azeotrope
0.3
and
dis­
This r e s u l t proves
0.06U
that
mole f r a c t i o n b r o m i n e .
mole f r a c t i o n bromine s o l u t i o n s i m i l a r l y
i s formed between
0.01*9
and
0*022
mole
fraction
bromine*
If
f
McCabe a n d T h i e l e s m e t h o d i s a p p l i e d t o F i g u r e 2,
and i f i t
i s remembered t h a t a t t o t a l r e f l u x t h e o p e r a t i n g l i n e c o i n c i d e s w i t h t h e
diagonal,
1 3
' i t i s s i m p l e t o c o u n t t h e number o f t h e o r e t i c a l
plates
n e c e s s a r y t o a c h i e v e a g i v e n s e p a r a t i o n o f t h e above s o l u t i o n s .
a p p l y i n g t h i s method, i t i s e v i d e n t t h a t about t h r e e or f o u r
p l a t e s w o u l d be r e q u i r e d t o go f r o m
or from
0.01*9
to
0.022
0.3
to
0.06U
mole f r a c t i o n b r o m i n e .
By
theoretical
mole f r a c t i o n bromine
The r e l a t i v e l y
large
number o f p l a t e s r e q u i r e d f o r t h e l a t t e r s m a l l s e p a r a t i o n i s d u e t o t h e
n e a r l y asymptotic approach t o t h e d i a g o n a l noted above.
comes more d i f f i c u l t ,
t h a t of pure s o l v e n t .
Separation be­
f o r t h i s r e a s o n , as t h e c o m p o s i t i o n approaches
I t i s v e r y p r o b a b l e t h a t t h e s m a l l column u s e d ,
h a v i n g a p a c k e d s e c t i o n o f o n l y a b o u t 1*0 c e n t i m e t e r s i n l e n g t h , h a s n o
more t h a n f o u r t h e o r e t i c a l p l a t e s .
I n c o m p l e t e s e p a r a t i o n , t h e n i s due
not to the formation o f an azeotrope, b u t to the f a c t that a f r a c t i o n ­
a t i n g c o l u m n h a v i n g a much l a r g e r number o f t h e o r e t i c a l p l a t e s w o u l d be
^ B a d g e r a n d McCabe, E l e m e n t s o f C h e m i c a l E n g i n e e r i n g , S e c o n d
e d i t i o n , (New Y o r k a n d L o n d o n ! M c G r a w - H i l l Book Company, I n c . , 1936),
p . 357.
25
r e q u i r e d f o r complete
separation*
The f a c t t h a t no a z e o t r o p e
prising.
If
i s formed i n t h i s system i s not
sur­
the d i f f e r e n c e between the r e s p e c t i v e b o i l i n g p o i n t s o f
the
two components o f a m i x t u r e i s l a r g e , p o s i t i v e d e v i a t i o n f r o m R a o u l t ' s
l a w m u s t be v e r y l a r g e ,
i n order t h a t the t o t a l vapor pressure o f
some
m i x t u r e may e x c e e d t h e v a p o r p r e s s u r e o f t h e p u r e l o w - b o i l i n g c o m p o n e n t .
The b o i l i n g p o i n t c u r v e w i l l n o t e x h i b i t a m i n i m u m ( a z e o t r o p e )
the
unless
c o r r e s p o n d i n g v a p o r p r e s s u r e - c o m p o s i t i o n c u r v e h a s a maximum.
The
d i f f e r e n c e between t h e b o i l i n g p o i n t s o f t r i c h l o r o m o n o f l u o r o m e t h a n e
b r o m i n e i s 35.2
degrees
centigrade.
T h e r e a p p e a r s t o be some e v i d e n c e
t h a t azeotrope
p o s s i b l y occur i n t h i s system, however.
formation could
Using H i l d e b r a n d ^
method,
1
S p i c e r and Meyer ^ found t h a t the d i f f e r e n c e between t h e i n t e r n a l
s u r e s o f b r o m i n e a n d b e n z o t r i f l u o r i d e was
27UO
atm.
Even t h o u g h
1 2
pres­
the
b o i l i n g p o i n t o f b e n z o t r i f l u o r i d e i s h& d e g r e e s h i g h e r t h a n t h a t
bromine, an azeotrope
and
of
i s formed i n the system b r o m i n e - b e n z o t r i f l u o r i d e .
U s i n g t h e same m e t h o d , i t was f o u n d t h a t t h e d i f f e r e n c e
between t h e
i n t e r n a l p r e s s u r e o f t r i c h l o r o m o n o f l u o r o m e t h a n e and bromine i s
2786
S i n c e i n t h e absence o f hydrogen b o n d i n g t h e d i f f e r e n c e
internal
1
i n the
p r e s s u r e s o f t h e c o m p o n e n t s ^ i s an i n d i c a t i o n o f t h e amount o f
f r o m R a o u l V s l a w t o be e x p e c t e d ,
i s more l i k e l y t o e x h i b i t a n a z e o t r o p e
1
2
J.
(New Y o r k :
1
i t appears ^
deviation
to follow that this
H . H i l d e b r a n d , S o l u b i l i t y o f N o n - E l e c t r o l y t e s , Second
R e i n h o l d P u b l i s h i n g C o r p o r a t i o n , 1936), p p . 98-106.
and M e y e r , o £ .
c i t . , p.
937.
^Ewell,
H a r r i s o n and B e r g , l o c *
cit.
page
29.
system
than i s the system bromine-
^Spicer
^See
atm.
edition,
26
benaotrifluoride.
The l i k e l i h o o d o f r e a c t i o n b e t w e e n t h e s o l v e n t a n d b r o m i n e
v e r y s m a l l , because
the solvent i s already
s a t u r a t e d w i t h halogens
h i g h e r e l e c t r o n e g a t i v i t y , whose c a r b o n - h a l o g e n b o n d e n e r g i e s
than t h a t o f the carbon-bromine bond.
is
are
of
larger
The s m o o t h n e s s o f t h e t w o e q u i l i b ­
r i u m d i a g r a m s i s a l s o an i n d i c a t i o n t h a t no r e a c t i o n t a k e s p l a c e .
A
t e s t f o r r e a c t i o n was n o t made, f o r p u r e s o l v e n t was n o t s u c c e s s f u l l y
separated from mixtures w i t h bromine*
The S y s t e m B r o m i n e - 1, l - d i c h l o r o - 2 , 2 - d i f l u o r o e t h a n e . — E q u i l i b r i u m
grams f o r t h i s s y s t e m a r e p r e s e n t e d i n F i g u r e s h a n d 5>.
dia­
Figure k is
t e m p e r a t u r e - c o m p o s i t i o n d i a g r a m c o r r e s p o n d i n g t o F i g u r e 1,
a
discussed
a b o v e , and F i g u r e 5 i s a v a p o r c o m p o s i t i o n - l i q u i d c o m p o s i t i o n d i a g r a m
c o r r e s p o n d i n g t o F i g u r e 2,
above*
system e x h i b i t s a b o i l i n g p o i n t a t
It
i s e v i d e n t from Figure k t h a t
I+9#6° C , 9*2
degrees l o w e r than
b o i l i n g p o i n t o f the l o w e s t - b o i l i n g pure component.
Liquid mixtures of this kind,
d i s t i l unchanged a t a d e f i n i t e t e m p e r a t u r e
That the b o i l i n g p o i n t depression a t
greater
mole
I n F i g u r e 5 i t i s seen t h a t the curve crosses
diagonal at t h i s composition*
are c a l l e d azeotropic
the azeotrope
7 a n d 8*
the
which
mixtures.
s h o u l d be
i n t h i s system t h a n i n the system f o l l o w i n g , i s expected
the data presented i n Tables
from
Since the b o i l i n g p o i n t s o f
c o m p o n e n t s o f t h i s s y s t e m d i f f e r o n l y b y 0.2
degrees,
a very small
t i v e d e v i a t i o n f r o m R a o u l t ' s l a w s h o u l d p r o d u c e an a z e o t r o p e .
l a r g e r i n c r e a s e i n volume on m i x i n g , and g r e a t e r
the
At this boiling
p o i n t m i n i m u m , b o t h l i q u i d a n d v a p o r h a v e t h e c o m p o s i t i o n 0.581
f r a c t i o n bromine*
this
cooling effect
the
posi­
The
observed
on m i x i n g t h e components o f t h i s s y s t e m , i n d i c a t e t h a t t h e p o s i t i v e
27
f
deviation from Raoult s law i s larger
The d i f f e r e n c e
these
than i n the
system f o l l o w i n g .
i n i n t e r n a l p r e s s u r e b e t w e e n b r o m i n e and e a c h o f
s o l v e n t s a s c a l c u l a t e d b y H i l d e b r a n d ^ m e t h o d , ^ seems t o be i n ­
consistent with t h i s larger deviation from Raoult's
ence was f o u n d t o be
2737
23UO
law.
This
differ­
atm f o r l , l - d i c h l o r o - 2 , 2 - d i f l u o r o e t h a n e ,
atm f o r l , 2 , 2 - t r i c h l o r o - l , l - d i f l u o r o e t h a n e .
However,
we m u s t
c o n s i d e r t h e e f f e c t o f h y d r o g e n b o n d i n g , w h i c h i s u s u a l l y more
1
than i n t e r n a l pressure d i f f e r e n c e s . ?
i n the l i t e r a t u r e ,
important
B o t h o f t h e s e compounds p r o b a b l y
f o r m weak h y d r o g e n b o n d s b e t w e e n a d j a c e n t m o l e c u l e s .
evidence
There i s
ample
i n d i c a t i n g t h a t weak h y d r o g e n b o n d f o r m a ­
t i o n w i t h t h e use o f a h y d r o g e n atom a t t a c h e d t o a c a r b o n atom o f
1 0
h a l o g e n a t e d h y d r o c a r b o n m o l e c u l e can t a k e p l a c e . *
chloroethane
and
F o r example
forms complexes w i t h e t h e r by hydrogen b o n d i n g .
a
penta-
That
this
a s s o c i a t i o n between l i k e molecules by hydrogen bonding i s weak, i s
dicated by the f a c t t h a t n e i t h e r
water.
in­
o f t h e s e compounds i s v e r y s o l u b l e
in
Because C H C I 2 C H F 2 c o n t a i n s t w o h y d r o g e n a t o m s , a n d one o f
these
h y d r o g e n atoms i s a t t a c h e d t o a c a r b o n a t o m t h a t h a s t w o f l u o r i n e
atoms
a t t a c h e d t o i t , p o s s i b i l i t i e s o f h y d r o g e n bond f o r m a t i o n appear
greater
i n t h i s compound t h a n i t
i s i n CHC^CT^Cl.
If
this is
t o be
true,
more h y d r o g e n bonds w i l l be b r o k e n when b r o m i n e i s i n t r o d u c e d i n t o
^Hildebrand,
^Ewell.
loc.
this
cit.
H a r r i s o n and B e r g , l o c .
cit.
S . G l a s s t o n e , T r a n s , F a r a d a y S o c . 33, 200 (1937); D. B . McLeod
a n d F . J . W i l s o n , I b i d . T l T T 59b (1935TT"G."T. Z e l l h o e f e r , M. J . C o p l e y ,
a n d C. S . M a r v e l ,
Chem. S o c . , 60, 1337 (1938); G. F . Z e l l h o e f e r
a n d M. J . C o p l e y , I b i d . 65Tl3UJTl93^T.
l 8
TTlm.
28
s o l v e n t , t h a n a r e b r o k e n when b r o m i n e i s i n t r o d u c e d i n t o s o l v e n t o f t h e
following system.
T h i s b r e a k i n g o f hydrogen b o n d s , causes a n i n c r e a s e
i n t h e p a r t i a l molar volume and vapor p r e s s u r e o f t h e s o l v e n t i n i t s
m i x t u r e s , and t h e r e f o r e a p o s i t i v e d e v i a t i o n from R a o u l t * s l a w .
I n the
l i g h t o f the p o s s i b i l i t y o f hydrogen bonding, i t i s n o t s u r p r i s i n g t h a t
i n c r e a s e i n volume o n m i x i n g i s g r e a t e r w i t h t h e components o f t h i s
system, and t h a t t h e b o i l i n g p o i n t depression a t t h e azeotrope i s l a r g e r
i n t h i s system t h a n i n t h e system f o l l o w i n g .
The r e s u l t of
t h e t e s t f o r r e a c t i o n between t h e components o f
t h i s s y s t e m was n o t c o n c l u s i v e , b u t s u p p o r t s t h e c o n t e n t i o n t h a t n o r e ­
a c t i o n takes place.
A n e x a m i n a t i o n o f T a b l e 6 a n d F i g u r e 3,
indicates
t h a t t h e r e f r a c t i v e i n d e x o f s a m p l e # 1 was w e l l w i t h i n t h e r a n g e o f
h i g h e r - b o i l i n g f r a c t i o n s o f CHC12CHF2*
I t i s evident t h a t i n separating
s o l v e n t f r o m i t s b r o m i n e m i x t u r e t h e s o l v e n t was f r a c t i o n a t e d , a n d
sample # 1 , b e i n g t a k e n f r o m t h e l a s t p o r t i o n o f l i q u i d t o l e a v e t h e
drying s t i l l p o t , contained the highest b o i l i n g f r a c t i o n o f f r a c t i o n
number
8.
That
fraction
number
ing l i q u i d i s n o t unexpected.
8 should contain
That
traces o f higher
the refractive
boil­
i n d e x o f sample # 2 ,
c o l l e c t e d a f t e r removing o n l y about two m i l l i l i t e r s o f l i q u i d from t h e
b o t t o m o f t h e c o l u m n , was much c l o s e r t o t h e r e f r a c t i v e i n d e x o f f r a c t i o n
number 8 b e f o r e c o n t a c t w i t h b r o m i n e , i s i n d i c a t i o n t h a t o n l y a t r a c e o f
h i g h e r b o i l i n g l i q u i d was p r e s e n t .
The s m o o t h n e s s o f t h e e q u i l i b r i u m c u r v e i n F i g u r e s k a n d 5 i s
further
i n d i c a t i o n t h a t no r e a c t i o n took p l a c e .
The S y s t e m B r o m i n e - 1 , 2 , 2 - t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e . — F i g u r e s 7 a n d 8
are t h e e q u i l i b r i u m diagrams f o r t h i s system.
I t c a n be seen f r o m
29
Figure
7
t h a t an azeotrope
having a composition o f
bromine, and a b o i l i n g p o i n t o f
F i g u r e 8, i t c a n b e s e e n t h a t
5U.6
0
0.7U7
mole
fraction
C i s formed i n t h i s system.
In
the vapor-composition v s . liquid-composi­
t i o n c u r v e c r o s s e s t h e d i a g o n a l a t 0.7U7 m o l e f r a c t i o n b r o m i n e *
From t h e f i g u r e s c i t e d above f o r t h e system b r o m i n e - b e n z o t r i f l u oride,
i t appears t h a t azeotrope
system.
f o r m a t i o n s h o u l d be e x p e c t e d i n t h i s
This system has a d i f f e r e n c e
o f o n l y 1 3 . 0 degrees between t h e
b o i l i n g p o i n t s o f t h e components, and a d i f f e r e n c e
the estimated i n t e r n a l pressures.
h$*0
internal
of
2737
atm between
The s y s t e m c i t e d h a s a d i f f e r e n c e o f
d e g r e e s between b o i l i n g p o i n t s , and a d i f f e r e n c e
o f 271*0 a t m i n
pressures.
I n making t h i s c o m p a r i s o n , i t was n o t i c e d t h a t t h e i n c r e a s e i n
volume on m i x i n g b e n z o t r i f l u o r i d e a n d bromine as r e p o r t e d b y S p i c e r and
M e y e r , was many t i m e s g r e a t e r
system.
t h a n t h e change i n volume f o u n d w i t h
Since t h e i n t e r n a l p r e s s u r e s o f b e n z o t r i f l u o r i d e and 1 , 2 , 2 -
t r i c h l o r o - 1 , 1 - d i f l u o r o e t h a n e a r e e s s e n t i a l l y t h e same, i t f o l l o w s
benzotrifluoride
pound.
will
this
must be more
highly associated than i s
the
latter
that
com­
The c o n c l u s i o n t h a t b e n z o t r i f l u o r i d e m o l e c u l e s a r e a s s o c i a t e d
a l s o e x p l a i n t h e i n c o r r e c t c o n c l u s i o n drawn i n comparing t h e
system b r o m i n e - t r i c h l o r o m o n o f l u o r o m e t h a n e w i t h t h e system broraineb e n z o t r i f l u o r i d e o n p a g e 25.
The b e n z o t r i f l u o r i d e m o l e c u l e s a r e p r o b a b l y
a t t r a c t e d t o each o t h e r t h r o u g h d i p o l e
association.
The r e s u l t o f t h e t e s t f o r r e a c t i o n b e t w e e n b r o m i n e a n d 1 , 2 , 2 t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e was n o t c o n c l u s i v e .
however,
t h a t no r e a c t i o n o c c u r r e d .
This t e s t
indicates^
The argument i s s i m i l a r t o t h a t
p r e s e n t e d f o r absence o f r e a c t i o n between t h e components o f t h e l a s t
30
system.
I n s p e c t i o n o f T a b l e 6 and F i g u r e 6 shows t h a t t h e
i n d e x o f s a m p l e #1 was w e l l w i t h i n t h e r a n g e
of s l i g h t l y higher-boiling fractions.
g r e a t l y d i f f e r from the r e f r a c t i v e
F i g u r e 6«
of the r e f r a c t i v e
I n f a c t , t h e f i g u r e does
i n d e x o f f r a c t i o n number 9
The r e f r a c t i v e
i n d e x o f s a m p l e #2
from t h a t o f t h e o r i g i n a l s o l v e n t w i t h i n the range of
The i n d i c a t i o n i s t h a t t h e s l i ^ i t
index a f t e r
indices
not
of
F r a c t i o n number 9 was i n c l u d e d i n t h e s o l v e n t m i x e d w i t h
bromine f o r t h i s t e s t .
error.
refractive
differs
experimental
change o b s e r v e d i n
refractive
c o n t a c t w i t h b r o m i n e , was due t o f u r t h e r f r a c t i o n a t i o n ,
n o t t o r e a c t i o n between bromine and t h e
In general,
systems s t u d i e d are
and
solvent.
the experimentally obtained r e s u l t s from a l l
the
i n a c c o r d w i t h what m i g h t have been p r e d i c t e d
a c o n s i d e r a t i o n of the p r o p e r t i e s o f these
systems.
from
APPENDIX I
TAELES AND FIGURES
31
Table 1.
Temperature
°C
V a p o r - L i q u i d E q u i l i b r i a D a t a f o r t h e System
B r o m i n e - T r i c h l o r omonofluoromethane•
Mole F r a c t i o n Bromine
i n Vapor
Mole F r a c t i o n Bromine
i n Liquid
23.6
0.000
0.000
23.7
0.022
0.031
28.1
0.21*9
0.506
29.2
0.292
0.597
3U. 8
o.ia6
0.823
39.6
0.520
0.911
1*1.2
0.563
0.925
50.5
0.80)4
0.977
58.3
1.000
1.000
F r a c t i o n a l d i s t i l l a t i o n o f a s o l u t i o n , which i n the e q u i l i b r i u m
s t i l l p r o d u c e d v a p o r t h a t w a s 0.2 m o l e f r a c t i o n b r o m i n e a n d l i q u i d t h a t
was 0.1* m o l e f r a c t i o n b r o m i n e , p r o d u c e d a d i s t i l l a t e t h a t was O.O6I4
mole f r a c t i o n b r o m i n e .
U s i n g t h e same c o l u m n , f r a c t i o n a l d i s t i l l a t i o n
o f 0.0l;9 m o l e f r a c t i o n b r o m i n e s o l u t i o n p r o d u c e d a 0.022 m o l e f r a c t i o n
d i s t i l l a t e a n d a 0.11° m o l e f r a c t i o n r e s i d u e .
32
T a b l e 2.
Fractional Distillation o f
1,l-dichloro-2,2-difluoroethane•
Temperature
°C
(uncorr.)
E s t i m a t e d Volume
Distillate i n ml
52.9
0
1
57.6
18
1*3773
2
58.0
3U
1.3781
3
58.3
70
1.3779
h
58J4
10U
1.3776
5
58.5
11+9
1.3772
6
58.6
183
1.3770
7
58.7
218
1.3769
oo
Fraction
Number
59.0
252
1.3769
9
59.U
267
1.3772
10
59.9
297*
1.3879*
Liquid
before f r a c t i onation
R e f r a c t i v e Index
a t 25° C
1.3780
The b o i l i n g p o i n t o f f r a c t i o n number 7 was d e t e r m i n e d i n t h e
e q u i l i b r i u m s t i l l a t 760 mm p r e s s u r e , a n d f o u n d t o b e 59.2° C . T h i s
v a l u e c a n be u s e d t o c o r r e c t t h e u n c o r r e c t e d t e m p e r a t u r e r e a d i n g s g i v e n
in this table.
* T h e r e s i d u e i n t h e d i s t i l l i n g f l a s k was a d d e d t o f r a c t i o n
number 10 b e f o r e t h e s e v a l u e s w e r e d e t e r m i n e d .
33
T a b l e 3.
Temperature
°C
V a p o r - L i q u i d E q u i l i b r i a Data f o r t h e System
Bromine- l , l - d i c h l o r o - 2 , 2 - d i f l u o r o e t h a n e .
Mole F r a c t i o n Bromine
i n Vapor
Mole F r a c t i o n Bromine
in Liquid
59.0
0.000
0.000
57.0
0.113
0.01*6
$k.h
0.21*6
0.123
53.7
0.293
0.1ft
51.2
O.Wtf
0.307
5o.o
0.559
0.509
1*9.9
0.565
0.5U2
1*9.7
0.578
0.567
1*9.6
0.531
0.581
1*9.8
0.622
O.691
51.0
0.702
0.825
52.2
0.762
0.893
55.5
0.882
0.972
53.8
1.000
1.000
3k
Temperature
°C
(uncorr,)
Estimated Volume
D i s t i l l a t e in ml
70.1
0
1
70,9
17
1.3917
2
70.9
3k
1.3910
3
71.0
67
1.3909
k
71.1
100
1.3908
5
71.1
133
1.3900
6
71.1
167
1.3899
7
71.2
200
1.3895
CO
Table 1.. Fractional D i s t i l l a t i o n of
1,2,2-trichloro-l,1-difluoroethane•
Fraction
Number
71.2
233
1.389U
9
71.2
268
1.3893
10
71.2
282
1.3892
11
71.2
291
1.3891
Drainage from fractionating column
Refractive Index
at 25° C
1.3979
35
T a b l e 5*
Temperature
°C
V a p o r - L i q u i d E q u i l i b r i a Data f o r t h e System
Bromine- 1 , 2 , 2 - t r i c h l o r o - l , 1 - d i f l u o r o e t h a n e *
Mole F r a c t i o n Bromine
i n Vapor
Mole f r a c t i o n Bromine
i n Liquid
71.8
0.000
0.000
70.0
0.085
0.026
63*6
0.359
0.163
57.8
0.553
0.3U2
56.5
0.638
0.1*79
55.2
0.722
0.61*1
5U.6
0.7U7
0.7U7
55.1
0.805
0.831*
56.5
0.903
0.91*9
58.8
1.000
1.000
36
T a b l e 6.
Solvent
fraction
Number
CHC1 CHF
2
2
CHC1 CF C1
2
Data on Tests f o r Evidence o f R e a c t i o n
2
8
k - 9
Refractive Index
a t 25° C B e f o r e
C o n t a c t w i t h Br2
1.3769
1.3900
Refractive Index
a t 25° C A f t e r
C o n t a c t w i t h Br2
Sample
# 1 , 1.3785
Sample
#2, 1.3773
Sample
# 1 , 1.3891
Sample
#2, 1.3899
37
T a b l e 7.
Solvent
Temp.
°C
CHC1 CHF
2
2
CHC1 CF C1
2
2
D a t a o n V o l u m e Changes O b s e r v e d on M i x i n g ,
Vol. of
Bromine
ml
Vol, of
Solvent
ml
Ideal Vol,
of Mixture
ml
Actual Vol.
of Mixture
ml
% Volume
Increase
29
1.71
2,25
3.96
U.03
1.8
31
2.37
1.60
3.97
3.98
0.3
N o t i c e a b l e c o o l i n g o c c u r r e d on m i x i n g , a n d t h e e f f e c t
t o be g r e a t e r f o r C H C 1 C H F .
2
2
appeared
38
Table
Component B . P .
at
8.
The P h y s i c a l P r o p e r t i e s o f t h e
Components o f t h e S y s t e m s I n v e s t i g a t e d .
Obs.
760
mm
Diff. in
B.P.'s of
Br2 and
Solvent
°C
°C
Br
58.8
2
CCI3F
CHC1 CHF
2
2
CHC1 CF C1
2
2
a
Company,
Density
Internal
Pressure
Estimate
gm/ml
atm
Diff. in
Estimated
Internal
Pressure
o f Br2 and
Solvent
atm
3.119
(20)
a
51*17
3.102
(25)
b
5387
23.6
35-2
1.U9U
(17.2)
c
2631
2786
59.0
00.2
l.U9k
(I6.1 )
d
3077
231*0
71.8
13.0
1.51*5 ( 2 5 )
2650
2737
I n t e r n a t i o n a l C r i t i c a l Tables,
1928), I I I , p . 20.
^Loc.
(t°C)
+
e
(New Y o r k :
McGraw H i l l Book
cit.
C
F.
Swarts,
Ber.,
d
F.
Swarts,
J.
e
A.
L . Henne a n d E. C . L a d d ,
26 R e f . ,
291
Chim. P h y s . ,
(1893).
20, 30 (1923).
J.
Am. Chem. S o c . ,
58, 1*03 (1936).
39
0.0
0.2
O.lj.
0.6
0.8
MOLE F R A C T I O N B R O M I N E
FIGURE
1
T E M P E R A T U R E - C O M P O S I T I O N D I A G R A M FOR THE
SYSTEM B r
- CCI3F A T 760 mm PRESSURE
2
O
v
a VAPOR,
O - LIQUID
• VAPOR A N D L I Q U I D
1.0
0.0
0.2
O.lj.
0.6
0.8
HOLE FRACTION BROMINE I N LIQUID
FIGURE 2
VAPOR-LIQUID EQUILIBRIUM DIAGRAM
FOR THE SYSTEM B r ? - CCl^F AT
760 mm PRESSURE
J
1.0
FRACTION NUMBER
?
4 - ^
*
7
60 [
I1.3780 6>
o
o
E
50
100
200
300
VOLUME I N M I L L I L I T E R S
FIGURE 3
FRACTIONAL DISTILLATION OF CHC1 CHF2
2
O = TEMPERATURE VS VOLUME
•
FRACTIONS
Z REFRACTIVE INDEX VS VOLUME
i4.,5,6,7
AND
8
WERE USED I N THIS
INVESTIGATION
1*2
65
6o F
o
o
Eh
55 h
50
^5
o.o
0.1;
0.2
0.6
0.8
MOLE F R A C T I O N B R O M I N E
FIGURE
lj.
T E M P E R A T U R E - C O M P O S I T I O N D I A G R A M FOR T H E
S Y S T E M Br
- C H C 1 G H F A T 760 mm PRESSURE
2
2
2
O s VAPOR, • = L I Q U I D
Q = VAPOR A N D L I Q U I D
1.0
1*3
0.0
0.2
0.1^
0.6
MOLE F R A C T I O N B R O M I N E
FIGURE
0.8
IN
LIQUID
$
V A P O R - L I Q U I D E Q U I L I B R I U M DIAGRAM
FOR T H E S Y S T E M B r
- CHCL?CHF 2
A T 760
mm PRESSURE
*
2
1.0
FRACTION NUMBER
VOLUME I N M I L L I L I T E R S
FIGURE 6
FRACTIONAL DISTILLATION OF CHCI2CF2CI
O =
• «
FRACTIONS
TEMPERATURE VS VOLUME
REFRACTIVE INDEX VS VOLUME
4 . 5 , 6 , 7 , 8 AND 9 WERE USED I N THIS INVESTIGATION
50 I
0.0
i
.
i
.
i
0,1+.
0,2
.
0,6
i
0,8
MOLE F R A C T I O N B R O M I N E
FIGURE
7
T E M P E R A T U R E - C O M P O S I T I O N D I A G R A M FOR T H E
SYSTEM B r
- C H C 1 C F C 1 A T 7&0 mm P R E S S U R E
2
2
2
O = VAPOR, • = L I Q U I D
© = VAPOR AND
LIQUID
1
1,0
U6
0,0
0,2
0,6
O.lj.
MOLE F R A C T I O N BROMINE
FIGURE
0,8
IN
LIQUID
8
V A P O R - L I Q U I D E Q U I L I B R I U M DIAGRAM
FOR T H E S Y S T E M B r
CHC1 CF C1
A T 7o0 mm P R E S S U R E
*
2
P
P
1.0
k7
FIGURE 9
EQUILIBRIUM S T I L L
a DISTILLATE CHAMBER; b FLASH BOILER; 0 RESIDUE CHAMBER;
d VAPOR L I N E ;
e , a CONDENSERS;
f , f , f HEATING COILS;
g
COOLING C O I L ; h COLD TRAP;
i TWO-WAY STOPCOCK; J TO PRESSURE
TANK; k TO WATER ASPIRATOR;
1 NO-LUB STOPCOCKS; m DISTILLATE
CHAMBER DELIVERY TUBE; n RESIDUE CHAMBER DELIVERY TUBE;
o,
O STANDARD TAPER GROUND-GLASS JOINTS; p THERMOCOUPLE WELL
U8
FIGURE 10
DRYING TRAIN
APPENDIX
II
SAMPLE CALCULATIONS
k9
APPENDIX
II
SAMPLE CALCULATIONS
A n a l y s i s o f a Sample
The c a l c u l a t i o n s i n v o l v e d i n m a k i n g e a c h a n a l y s i s i s
by the f o l l o w i n g
demonstrated
example:
Data
Weight o f weighing b o t t l e o f K I s o l u t i o n —
Weight o f w e i g h i n g b o t t l e and K I s o l u t i o n +
sample—
Weight o f sample —
Milliliters
of
0.2012 N Na2S203
1U.U818
gm
lf>.20£2
gm
0.723U
gm
standard s o l u t i o n
t o t i t r a t e t h e sample —
1U.8U
ml
Calculation
The r e a c t i o n s i n v o l v e d
2KI
2
+
Br
S °3 +
2
2
are:
=•
2
I
=
2
KBr t
I
2
IT
S 0 "i6
U
A l a r g e e x c e s s o f K I was m a i n t a i n e d t o r e d u c e t h e v o l a t i l i z a t i o n
of
iodine by the formation of t r i - i o d i d e i o n s :
i- +
Prom t h e s e c o n d e q u a t i o n i t
i
2
=
i
3
-
c a n be s e e n t h a t t h e
w e i g h t o f i o d i n e i s one a t o m i c w e i g h t .
equivalent
From t h e f i r s t e q u a t i o n i t
e v i d e n t t h a t one a t o m i c w e i g h t o f i o d i n e i s e q u i v a l e n t
t o one
is
atomic
weight of bromine.
I t follows then, that the equivalent weight of
bromine i s i t s atomic w e i g h t .
E q u i v a l e n t weights o f bromine =
Normality of
Na S203
2
Milliliters of
x
solution
Na2S203
1000
= 0.2012 x jjj^* = 0.002986
Moles o f bromine =
=
1/2 x E q u i v a l e n t w e i g h t s o f b r o m i n e
1/2 x 0.002986 = 0.0011*93
Weight o f bromine = E q u i v a l e n t weights o f bromine x
Equivalent weight o f bromine
- 0.002986 x 79.92 = 0.2386 gm
W e i g h t o f CHC1 CHF2 2
W e i g h t o f sample - W e i g h t o f bromine
- 0.723U - 0.2386 = 0.1*81*8 gm
M o l e s CHC1 CHF
2
2
_
-
W e i g h t o f CHC1 CHF
Molecular w e i ^ t o f
2
=
=
2
CH61 <^
2
0.003593
T o t a l m o l e s = M o l e s o f b r o m i n e + M o l e s o f CHC1 CHF2
2
= 0.0011*93 + 0.003593 = 0.005086
Mole f r a c t i o n bromine —
Moles o f bromine
T o t a l moles
_ 0.0011*93 _
n
9 o U
- o.oo5o86 - ° '
29U
2
51
Determination
o f Change i n Volume
on M i x i n g
Data
Volume o f b r o m i n e a d d e d —
1.71 m l
Volume o f
2.25
ml
U.03
ml
added-
CHC1 CHF2
2
A c t u a l volume o f m i x t u r e Calculation
I d e a l v o l u m e o f m i x t u r e = Volume o f b r o m i n e
+
Volume o f
CHCI2CHF2
added
=• 1.711 2.25 = 3.96
Volume i n c r e a s e — A c t u a l v o l u m e o f m i x t u r e - I d e a l v o l u m e o f m i x t u r e
= U.03 - 3.96 - 0.07
Per
i
c e n t volume i n c r e a s e =
n
c
ml
r
e
a
S
^
A
„
x
100
I d e a l volume o f m i x t u r e
= § g x K 0 = l.B
Estimation of Internal
Pressure
1 0
Data
Solvent
—
CHC1 CF C1
2
2
O b s e r v e d b o i l i n g p o i n t o f s o l v e n t a t 76O mm — 71.8°
D e n s i t y o f s o l v e n t a t 25°
C —
1.5U5
C
go/ml
Calculation
E n e r g y o f v a p o r i z a t i o n =•
AE
y
=
5280 + (2lw5
x atmospheric
p o i n t i n ° C)
=
M o l a r v o l u m e a t 25°
5280 +• (2U.5 x 71.8) - 7039 c a l
C = V = Molecular
weight
D e n s i t y a t 25°
C
boiling
v
I n t e r n a l pressure
=
2222- = 6U.19
109.7
V
6U.19 S
i
ml
x
la.29
1111
;
a t f f i
cal
=
2650
atm
cal/ml
53
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4